In a known design a disk brake comprises a brake disk rotating on and along with a hub of a wheel to be braked, onto which friction linings in the form of brake pads or friction linings are pressed from both sides. Said friction linings are mounted in a so-called brake caliper. The brake caliper is also referred to as a caliper and spans the brake disk. Activation of the brake takes place in general hydraulically using at least one brake piston as an actuator. In motor vehicles, as a rule partial disk brakes are used, i.e. disk brakes which only use part of surface of the disk as a frictional surface.
Furthermore, with automobiles so-called floating caliper brakes are preferably used. Floating caliper brakes have actuators on only one side of the disk in contrast to fixed caliper brakes. The design of the floating caliper brake enables the brake force on both sides of the brake caliper to be built up basically by only one actuator. The longitudinally displaceably mounted or floatingly suspended brake caliper mechanically transfers the pressure applied by only one actuator to the other side of the brake disk. Floating caliper brakes only need relatively little insta11ation space as a result of this design, so that a floating caliper brake with lower structure height in comparison to fixed caliper brakes can be positioned better. Furthermore, floating caliper brakes have high efficiency and are relatively simple in design and in maintenance. Thus friction- or friction linings can especially be changed in a short time.
In known disk brakes, hydraulically operated pistons are used as actuators, which can be displaced in suitable operating devices using hydraulic pressure. In the case of an electromechanically operated disk brake, an electromechanical actuator is used instead of a hydraulic cylinder.
In principle, with a disk brake having an electromechanical actuator there is no feedback regarding a brake force acting on a brake pedal, as is provided via the hydraulic circuit with conventional hydraulic brakes. Therefore it is particularly desirable with a disk brake having an electromechanical actuator—but also with hydraulically operated disk brakes-independently of their exact structural embodiment, to continuously and very accurately detect a brake force actually acting in operation.
Only on this basis can the disk brake be regulated reliably and with the necessary accuracy, in order to satisfy a braking demand specified by a user and also to be able to respond thereto as well as to be able to carry out slip-controlled braking (antilock braking control).
Various approaches are known from the prior art for determining the clamping force (normal force) of a disk brake, i.e. the force with which the friction linings in are forced against the brake in a direction normal to the surface of the disk brake. However, the clamping force is not proportional to the brake force (peripheral force) or the brake torque. Thus the coefficient of friction (μB) between the friction lining and the brake disk, which is dependent on conditions such as temperature, wetness, and dirt, and fluctuates during operation, is to be taken into account as a factor. The brake torque is proportional to the brake force with a so-called effective friction radius, which is likewise variable and cannot be accurately determined. Accordingly, for a hydraulically operated disk brake according to today's state of knowledge, because of the high degree of complexity of the processes, the variation of the brake torque cannot be reliably determined from the variation of the brake pressure.
Approaches for determining the clamping force of a disk brake usually build on an elastic expansion of the brake caliper (in a direction perpendicular to the surface of the disk brake (axial direction)). It is thus known that the expansion of the brake caliper is measured with a strip strain gauge, which is glued in a yoke area of the brake caliper, with which the brake caliper fits over the brake disk. Also in DE 10 2006 029 978 B3 a method and an apparatus for measurement of a normal force acting on a disk brake are disclosed. For this purpose a device is provided on the brake caliper of the disk brake, which measures the normal force using an elastic expansion of the brake caliper during clamping of the brake by measuring a shearing movement of part of the disk brake during expansion of the brake caliper.
A brake force measurement device for a friction brake with a frame caliper is known from DE 10 2005 013 142 AI, which measures a movement of the brake caliper during braking by means of a travel measurement device having two parts moving with respect to each other. Here one of the parts of the travel measurement device is always disposed on the movable brake caliper.
The object of the invention is to provide a brake mounting, an apparatus and a method by means of which during a braking process a measure of the brake force (peripheral force) acting on a disk brake or the brake torque acting on a disk brake can be continuously detected with an inexpensive means and with adequate accuracy.
The object is achieved according to the invention by the brake mounting, the apparatus, and the method as described herein.